A first chronology for the NEEM ice core
Author:
Rasmussen S. O., Abbott P., Blunier T., Bourne A., Brook E.ORCID, Buchardt S. L., Buizert C.ORCID, Chappellaz J., Clausen H. B., Cook E., Dahl-Jensen D., Davies S., Guillevic M.ORCID, Kipfstuhl S., Laepple T., Seierstad I. K., Severinghaus J. P.ORCID, Steffensen J. P., Stowasser C., Svensson A.ORCID, Vallelonga P.ORCID, Vinther B. M.ORCID, Wilhelms F., Winstrup M.ORCID
Abstract
Abstract. A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified in the Electrical Conductivity Measurement (ECM) and Dielectrical Profiling (DEP) records. Tephra horizons found in both the NEEM and NGRIP ice cores are used to test the matching based on ECM and DEP and provide additional horizons used for the time scale transfer. A thinning function reflecting the accumulated strain along the core has been determined using a Dansgaard–Johnsen flow model and an isotope-dependent accumulation rate parameterization. Flow parameters are determined from Monte Carlo analysis constrained by the observed depth-age horizons. In order to construct a chronology for the gas phase, the ice age–gas age difference (Δage) has been reconstructed using a coupled firn densification–heat diffusion model. Temperature and accumulation inputs to the Δage model, initially derived from the water isotope proxies, have been adjusted to optimize the fit to timing constraints from δ15N of nitrogen and high-resolution methane data during the abrupt onsets of interstadials. The ice and gas chronologies and the corresponding thinning function represent the first chronology for the NEEM core, and based on both the flow and firn modelling results, the accumulation history for the NEEM site has been reconstructed, providing the necessary basis for further analysis of the records from NEEM.
Publisher
Copernicus GmbH
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